1. Field of the Invention
The present general inventive concept relates to a method and apparatus to process an analog encoder signal, and more particularly, to a method and apparatus to process an analog encoder signal, which divides one period of an analog sinusoidal wave signal output from an analog encoder into a predetermined number of states, samples the analog sinusoidal wave signal, compares the analog sinusoidal wave signal with an output signal of the analog encoder, determines a present estimated state based on a recent state, and generates a quadrature signal to control a motor.
2. Description of the Related Art
In recent years, with rapid development in automatic control systems, processing signals output from various sensors is becoming more and more important to realize precise control operations.
FIG. 1 is a block diagram of a conventional apparatus for calculating a position of a printing paper. The apparatus includes an analog encoder 100, a quadrature signal generator 110, an inverter 120, a multiplexer (MUX) 130, an analog/digital (A/D) converter 140, and an absolute position calculator 150.
Referring to FIG. 1, the analog encoder 100 is connected to an axis of a motor and rotated together with the axis, and outputs two quasi-sinusoidal wave signals, each of which has a predetermined number of periods per rotation of the analog encoder 100, by a phase difference of 90°.
The quadrature signal generator 110 is connected to an output terminal of the encoder 100, receives a quasi-sinusoidal wave signal 101 from the encoder 100, and generates a quadrature signal 111 for obtaining coarse positional information, which is required to divide one period of the output signal into a plurality of states.
The inverter 120 obtains the output signal 101 from the encoder 100 and outputs an inverted output signal 121 of the output signal 101.
The MUX 130 receives the output signal 101, which is a quasi-sinusoidal wave signal, from the encoder 100 and the inverted signal 121 and outputs only one analog signal 131 based on the coarse positional information.
The A/D converter 140 converts the analog signal 131 into a digital signal 141 and transmits the digital signal 141 to the absolute position calculator 150.
The absolute position calculator 150 receives the digital signal 141 output from the A/D converter 140 and the quadrature signal 111 output from the quadrature signal generator 110, obtains the coarse positional information from the digital signal 141 and precise positional information from the digital signal 141, and calculates a precise position of the motor as the motor rotates.
However, in the conventional case, analog/digital (A/D) converted values should be read in short periods to realize a precise control operation. This increases the burden of a central processing unit (CPU).